You're not expressing your idea as you should. Group job is not a custom tag color. Custom tag color is personal feature and it costs like 350 mils.
You're clearly talking about group job, and yes currently criminals and civilians has job colors on their name tags. So should we say they forgot to add same feature to law officers ? I don't know. It's actually a minor idea which hasn't lot of priority, but it's a fancy feature which could look great so why shouldn't it be a thing in-game ?
I don't have anything against that idea, and due to the statement above, I'm supporting that suggestion.